There are several models of depression that psychologists have arrived at from consideration of its potentially adaptive function. Some are weaker than others; some are mutually compatible. When I posted a Facebook link to the Wikipedia article giving an overview of a few of them, my friend Jonathan Tweet edited the sketchy intro. Here’s that article:

http://en.wikipedia.org/wiki/Evolutionary_approaches_to_depression

A brief comment thread followed my Facebook post, in which a couple of my friends were put off by this line of inquiry. They seemed to think that it was dismissive of the idiopathic complexity of the disease; they cited their own battle with depression, seemingly out of concern that their own experience might be overshadowed or discounted by a general theory. I respectfully think they missed the point. Here is my answer defending one model to a friend who read the article and wasn’t impressed; he argued that chronic depression didn’t seem to confer any survival benefit and therefore couldn’t be an adaptation.

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The social navigation theory in the list has deep implications. Unlike, say, hive insects, we have powerful minds and feel a keen struggle to promote our unique talents to the group, for its own good. We resist being put in our place, because no one but us can best discover our place. We have to desperately promote ourselves to each other, by building friendships, by politicking, and by competing. When we end up in the wrong occupation or social niche, when what we have to offer is being squandered one way or another, a deep unconscious process is triggered to raise the stakes, toward either resolve or depression, and either may effect a change that helps us realize our potential — or that gets us killed.

Nature doesn’t “care” if depression leads to angst and occasionally suicide if it tends to promote the survival of those closely related to the depressed person.

Some of the most wonderful, creative people are the most chronically depressed. They have unusual minds that make them especially isolated; they aren’t as easily satisfied as the rest of us. They undergo midnight journeys of the soul, desperate and ambitious, to bring us the fire we need to survive.

Chronic depression may very well be adaptive, and it may very well be tied to self-actualization and so-called spiritual growth as Jung and others have claimed. I personally think it is. These things are not mutually exclusive at all.